Remove keyword exceptions

These exceptions are just confusing as the grammar actually allows both 'der' and 'initial' (and also 'pure') to be used as the callee of a function call expression.

chapters/lexicalstructure.tex

@@ -108,7 +108,7 @@ \subsection{Names}\label{names}
 
 \subsection{Modelica Keywords}\label{modelica-keywords}
 
-The following Modelica \firstuse{keywords}\index{keyword} are reserved words and shall not be used as identifiers, with the exception of \lstinline!initial! which is a keyword in section headings, and \lstinline!der! which is a keyword for declaration functions, but it is also possible to call the functions \lstinline!initial! and \lstinline!der!:
+The following Modelica \firstuse{keywords}\index{keyword} are reserved words and shall not be used as identifiers:
 \begin{center}
 \begin{tabular}{l l l l l}
 \lstinline!algorithm! & \lstinline!discrete! & \lstinline!false! & \lstinline!loop! & \lstinline!pure!\\ \hline